The overarching goal of the proposed research is to determine the extent to which temperament disposition, in the context of family interaction patterns, contributes to the multifactorial liability to substance abuse in children derived from high risk (parental history of substance abuse; SA+) and low risk (normal parental history; SA-) families. Two groups consisting of SA+ (n=200) and SA- (n=200) families will be studied. First born and second born offspring will be 50% female and 50% male. In addition to 1,600 family members, first born offspring will select a friend to participate in the study yielding a total of 2,000 subjects. Time 1 assessment is scheduled when the first born is 10-12 years of age. Time 2 assessment is scheduled when the first born is 12-14 years of age. Time 3 assessment is planned when first born becomes 15-16 years of age. Measures tapping individual, family, and peer risk and protective factors are obtained on all subjects. Deviations in temperament are hypothesized to mediate the relationship between SA+ family history, family dysfunction, and dysfunctional discipline practices. The impact of first born's risk factors on second born's behavioral maladjustment are hypothesized to be mediated trough second born's temperament. Temperament induced maladaptive patterns of interaction among family members are hypothesized to propel the child towards affiliations with deviant peers augmenting the liability for early age substance use and abuse. Thus, this study is unique in attempting to disaggregate and analyze the liability for early age substance use and a diagnostic threshold of abuse from an interactional perspective that incorporates two well-established sets of risk factors; a) family history of substance abuse; and b) temperament disposition which has been shown to influence the developmental trajectory and accordingly produces behaviors which predisposes to substance abuse. The results of the proposed study will contribute toward a more comprehensive understanding of the development of substance abuse by incorporating both trans-generational and ontological perspectives.